He Comes Out of the Black Lake Quite Mad
by Dawn96
Summary: Regulus Black finds himself out of the cave but drowning. Hogwarts will keep him safe, says Dumbledore, and he can teach Charms since the war is over. But, Regulus hasn't stopped drowning and the face of Harry Potter, who looks too much like James Potter, makes Regulus think too much of a war he hasn't escaped.
1. 1

_AN: Just thought I'd separate the one-shot into two chapters to ease the reading (it was bugging me for the last few days!)_

* * *

 **1**

He comes out of the black lake quite mad, very much his mother's son.

They try to stop him screaming but he doesn't think they understand. He didn't think he could understand. How could they understand. Their rotten teeth had bitten into his skin- their gnarled nails into his flesh- their cold hands pulled his mind apart.

He vaguely sees the floor and wonders why it's not water and why he isn't drowning- then he remembers that he still is and he suffocates, lungs full with water, and coughs it all out on the floor.

He vaguely sees the Headmaster- vaguely sees McGonagall- but screams when Pomfrey comes at him in her white, white gown and a bottle of white, white draught.

He thinks they lock him up ( _he would certainly lock himself up, like an animal, unstable, quite mad)_ but he vaguely sees mouths talking and words being said. He tries to tell them that he's drowning and there are corpses- white, white corpses- pulling him to the ground.

"You're safe," says Dumbledore but Regulus always thought him daft anyway.

Pomfrey comes in with another sleeping draught but he can't swallow water. He has swallowed enough and his lungs are now saturated. He coughs it all out on the floor and drowns all over again.

It's only when he finds his face on a mirror that he sucks in a breath and realizes there's no water- no cave. He looks gnarled and dead and he tries to gouge his eyes out to stop seeing corpses. Pomfrey catches him in the act and tries to hold him but he stains her gown with blood.

She shushes him and coos and rocks him and he thinks of his mother with her yellowing eyes and gaunt skin and grating, gritting screech. He pulls away and clamps on his ears and screams; he's drowning in a lake of corpses and the walls as black as the walls of that house and there's nowhere to escape.

* * *

He teaches Charms when he's twenty because Dumbledore is daft and Regulus has nowhere to go.

(He has Grimmauld Place but it's drowning in the stench of his dead mother. He has Azkaban but it's occupied with his savage cousin and a brother he couldn't understand.

Then again, there was a lot he didn't understand: _the Dark Lord dead, a Boy Who Lived and a Charms classroom on the sixth floor)._

But he teaches Charms anyway: because Dumbledore is daft and Regulus has nowhere to go and he'd much rather think of floating feathers than drowning. And then, when the lesson is over and the seventh year girls giggle as they pass him by, he takes calming draught after calming draught to stop the corpses in his eyes and the water on his hands.

"I'm no Potions Master but I know there's only so much calming draught a person can take," says Minerva and he feels like he's thirteen and caught after curfew.

He sneers and walks past her but the calming draught he holds slips from his hand and he watches the water splatter across the floor. He almost screams- _but he doesn't_ \- but he cries instead- _even worse_ \- and she takes him to her office and offers him a biscuit.

"It will take time," she says sternly.

He tries to explain that he's still drowning- can't she see?- but he sounds mad even to his own ears so his bites his tongue and says nothing more.

* * *

He didn't think he'd care about the year Harry Potter started, but he can't help it when he sees James Potter sitting in his classroom without Sirius by his side. It makes him so sick he forgets the pain pulsing down his arm or the bruises shackled around his ribs. He takes five points from Gryffindor- he can't remember why, his mood is too foul- and he hears the class grumble about Slytherin teachers and prejudice.

(Apparently Severus has noticed Harry Potter as well and took off a good ten points. Regulus doesn't speak to Severus. Corpses and water are enough. He doesn't think his mind can take schoolboy memories of a bitter brother and red-haired mudbloods).

He goes to Hagrids for tea and watches Potter and Weasley walk down the grounds. Hagrid pours him a bowl beside a rock cake and gives him a dollop of firewhiskey.

(Eleven years ago, Hagrid did the same and gave him a wink: _you're allowed it now since yer a member o' staff._ Regulus had laughed and then cried and felt pathetic all over again: to think that a Black would accept the comfort of a gamekeeper. He felt a flush of shame at the thought and accepted the tea and sympathy.)

"You dun happen to have a few pictures of James and Lily do you?" asks Hagrid, looking out the small window. "Poor kid dun know anything about 'em."

Regulus almost says no, scathingly, because he remembers James Potter with Sirius beside him and it makes a jealous knot in his stomach. He also remembers Sirius in Azkaban, surrounded by Bella's cackles, whispering that it was ' _all his fault'_ over and over again.

But he says, "I'll look around," instead because he's too tired to be scathing and it's not that that kid's fault Regulus' own life is hell.

(Severus, it becomes apparent, thinks otherwise.)

* * *

Regulus doesn't mind Lockhart's incompetent appearance. For the first time, he is more annoyed at someone's idiocy than he is afraid of his own shadow. It is welcoming- even if the man is infuriating- and he even lets himself crack a smile at Minerva's exasperated expression and Severus' hostile one.

All until students are petrified and there is blood on the walls and poor parseltongued Harry Potter become all the school can talk about. He doesn't stay for Christmas because he can't stop trembling, so he stays in Grimmauld Place with Kreacher and ends up cleaning and cleaning and cleaning- the walls, the floors, the tables, the stairs, his hands, his hands, his hands, his hands.

They're red and raw and he sits in front of the fire, half wondering if swallowing coal would dry out the water in his lungs. Kreacher stops him from reaching out and gives him a mug of tea. He smiles at the elf and thanks him. Kreacher gives him a low bow and then a loving pat on his knee.

His mother's portrait screams from behind the curtain and Regulus has half the mind to scream with her.

When he goes back to Hogwarts after winter, it's to a missing student and a secret chamber and a giant basilisk snaking through the pipes. He also comes back to Cissa's son who has Lucius' mouth and almost hits him on the back of the head when he hears him hissing slurs. Instead, Regulus grabs him by the scruff of his neck and tells him to keep his mouth shut.

Draco is unhappy and so, of course, Cissa is unhappy which, in turn, makes Lucius unhappy. Regulus burns the letter feeling very happy indeed. He also feels very scared: because Draco is a little jerk but he is also a child and, in their world, children are in danger and the words they say can bite them in the back when they grow old.

Lockhart is pulled out of the chamber, his memory completely wiped, and, for a moment, Regulus feels almost jealous: because there are words he wishes he can take back, actions he wishes he can erase and memories he wishes he can forget. He thinks of explaining that to Draco but the boy is too much like his father and too little like his mother that Regulus can't stand him.

* * *

He doesn't recognize Lupin when he sees him at the high table but Lupin recognizes him. He gives him a tired smile and a tired wave and Regulus can only imagine what twelve years of estranged loneliness can do to a person.

"You look awful," he says.

Lupin laughs pleasantly. "It's good to see you."

Yeah right, thinks Regulus, but says nothing. Instead, he looks at the picture of Sirius laughing on the front page of the Daily Prophet and begins a ritual of washing his hands and tracing the scars that run up his arms and all across his chest and legs. He feels flesh underneath his nails and wakes up thinking his teeth are rotten and have fallen out. He dunks his head in a bucket of cold water to wake up and, for a second, he thinks he's a corpse in the black lake.

He drinks calming draught after calming draught until he's sure he can't breathe- but that doesn't matter since corpses don't need to breathe anyway.

Pomfrey finds him on the floor in a heap of sweat and blood and she hugs him, like she did all those years ago, but he pulls away, like he did all those years ago, because there is blood all over her gown.

Then, he overhears them walking outside his empty classroom.

"I think it's not a bad idea to ask him, Harry," says Hermione.

"Are you mad?" says Ron, "Professor Black will bite your head off before you get a word in!"

"Really, Ronald?"

" _Is it okay if I ask you about this insane relative of yours who I think is out to kill me?"_ says Ronald in a mockingly, shrill voice. "Sounds great, doesn't it?"

Harry says nothing. Then: "The Prophet said it's his brother."

"Can see the resemblance," snorts Ron. "They both look a bit unhinged."

Hermione reprimands him but Harry says nothing again.

* * *

There's a boggart in the staff room and it turns into leeching corpses. They burst out of the closet with white, white arms and black, black nails, covered in cold, cold water and doused in thick, thick rot. He can't speak because he's drowning again and he can't breathe because of the water in his lungs. It's dark because he's in a cave again and there's no way out.

But the corpses become a full moon before it becomes a balloon that hides back in the closet. Lupin is in front of him, looking very sympathetic, and Regulus leaves without another word.

His thinks his nails are black and rotten so he pulls them off and douses his hand in water.

* * *

He finds out about Severus and Augusta Longbottom's medieval wardrobe when he's teaching sixth years. A gaggle of girls come up to him after class and giggle about it before cheekily ask him to Hogsmeade with them.

"You can say you're supervising, sir," she insists and he looks at her like she has three heads.

"Get out," he says and he pushes them through the door.

"Please, professor!"

He closes the door and shakes his head because he never really understood sixteen-year-old girls when he was sixteen let alone thirty-two. He sees a picture of Sirius snarling on the front page of the Prophet and thinks that he never really understood much of anything: his family, his brother, the Dark Lord, the war, the water, the corpses, the cave.

He sets the paper on fire and lets smoke fill up the room.

* * *

He sees Potter wandering about at night with a peculiar parchment and demands the boy turn out his pockets.

"Just a spare piece of parchment," says Harry, aggravated.

Regulus doesn't like the attitude. Harry's face reminds him too much of James Potter which reminds him of Sirius which makes everything angrily confusing. He touches the parchment with his wand and watches the ink appear.

 _Mr Padfoot would like to register his surprise… a soft idiot… ever became a professor!_

 _Mr Moony would like to add…_

 _Mr Prongs can't believe…_

 _Mr Wormtail bids his goodnight to the soft idiot…_

Before he could do something insanely impulsive- take a thousand points off Gryffindor, scream into an abyss, shatter, break- Lupin appears and takes the parchment from Regulus' pale and trembling hands.

"I'm just going to take Harry here… a quick word… essay that's due," says Lupin, "if you'll excuse us… Goodnight."

Regulus stands in the dark, his wand long gone out, trying to undo the thoughts racing through his head.

"Are you daft?" says the portrait of a little wizard in a pointy, yellow hat. "Put that light out!"

Regulus sneer and keeps an orb of light glowing in corridor.

* * *

The story is longwinded but, from what he gathered, Lupin had a rough night and Severus was going to be awarded an Order of Merlin, Second Class, for catching a notorious mass murderer. It is like a school prank gone wrong with no one left laughing.

Sirius is locked in a tower and Dementors are crowding in for their Kiss. Regulus thinks of aiming a killing curse at a smug Severus just to get arrested. Maybe, that way, the Dememtors will suck out his soul too and it'd all be over. He doesn't mind dying beside his estranged brother, on dry ground, away from all things cold and wet.

He sneaks up to the tower and finds Sirius huddled behind bars. They look at each other and say nothing. He almost walks away but his knees weaken and he kneels next to the bars and reaches out with his scarred, scarred hands. Sirius takes it, his hand bony and his skin filthy, and they hold each other for a moment, for two, before Regulus has to stand up and pull himself away.

And then he finds out that Sirius broke out and that Harry Potter gets a new firebolt and that Lupin is a werewolf who is about to get the sack.

"I'm sure we'll see each other again," says Remus politely.

"Sure," says Regulus, "we'll grab a few pints but you'll be paying. That way, we'll both be sure we're never seeing each other again."

Remus laughs, his face all scarred up, and Regulus wonders how he does it. Remus gives him a pat on the shoulder as he walks out and Regulus remembers the sandy-haired boy who walked beside James Potter, smiling, scarred face not as scarred, sad eyes not as sad.

" _All you have, Moony, is a furry little problem," James Potter had said. "Nothing more, nothing less!"_

" _Half the school is under the impression I've got a badly behaved rabbit."_

" _Rabbits are cuter than wolves. That can score you points with the ladies."_

" _Merlin, do you even hear yourself?"_

"He's really innocent?" swallows Regulus., thinking of his brother.

Remus smiles sadly.

* * *

The Quidditch World Cup is around the corner and Regulus can't bring himself to go. He locks himself in his house and cleans the house: the floors, the walls, the windows, the furnaces, the banisters and the stairs. Then, he fills a bathtub with boiling water and almost cleans off his skin. Kreacher finds him and stops him and shrieks.

 _The water will hurt Master- Master mustn't wash himself with that water- please Master- Master mustn't- it's dangerous-_

He snaps out of his nightmare and apologizes and says that it was a spell gone wrong. That he hadn't meant it. That he wasn't aware. He didn't think he was. He didn't know if he was.

He puts on the wireless while Kreacher cooks and hears about the disaster at the World Cup. His arm burns when he sees the picture of the mark hanging above the Prophet and his stomach twists when he gets a letter from Dumbledore, warning. He goes back to Hogwarts in time for the school year and almost vomits onto the high table when he sees Mad-Eye Moody stalk into the Great Hall at the welcoming feast.

He suddenly remembers Evan Rosier, with his blonde hair and raucous laugh, before he had been blown to bits. He remembers Rosier's mother pulling out her hair in the funeral.

Moody stares at Regulus and Regulus stifles a shudder.

* * *

It comes as no surprise that Harry Potter is the fourth champion. That boy has as much as luck as his parents did before they were murdered.

He is surprised, however, when he hears Diggory's name being called. He's a talented boy but Regulus doesn't like him much. He never did like Hufflepuffs. He catches sight of Draco leering and thinks he doesn't like Slytherins either.

"Poor boy," says Minerva beside him, watching fourteen-year-old Harry Potter standing next to the other three champions.

Regulus hums.

Sirius writes to him that night. The words don't make any sense not because they are badly written, but because Regulus finds it hard to concentrate. He can grade papers and write on blackboards and skim through essays but letters from his brother are too nonsensical. They didn't fit into the timeline of his brain. The timeline that states that he was ripped apart, in a cave, surrounded by water, surrounded by the dead. He shouldn't be reading letters. He shouldn't be grading papers. He shouldn't be breathing with lungs saturated with water.

Regulus almost ignores the letter but can't. He writes back and says he'll try to protect the boy, if that's what his brother meant.

Sirius writes back. _Of course that's what I mean, bloody idiot. With a head like that on your shoulders, are you even supposed to be teaching…?_

Regulus scoffs and keeps the letter in his pocket, closest to his heart. For a moment, everything feels normal. Then, he takes some calming draught to stop his hands from trembling.

* * *

The dragon is too ostentatious and the gillyweed is impressively ingenious but it is the maze that is crowned victor of creativity. He stands beside Dumbledore as Potter bleeds onto the floor and Mad-Eye Moody turns into a ragged version of his old friend.

"They'll come for you, Reg!" laughs Barty, "He'll rip you apart when He finds out you're alive!"

And Regulus can only stare at the shadow of his old friend and think of when Barty used to fall asleep and drool all over the textbooks in the common room.

Severus stays behind, Dumbledore drags Harry up to his office and Regulus doesn't know where he is anymore. He helps Pomfrey clean Cedric Diggory in the Hospital Wing. For once, a dead body doesn't unnerve him. He doesn't know why. Maybe because the body is still warm and not yet cold. It still had a remnant of life. It made Mr Diggory's howls all the more painful.

It reminded him of when his mother had howled the night Sirius had run away.

He finds Sirius outside Dumbledore's office, ready to alert an Order Regulus doesn't want to remember. They are not separated by prison bars but they are separated by time.

"He saw James and Lily," says Sirius quietly, referring to what Potter had seen in the graveyard.

Regulus almost sneers. Of course that's what Sirius thinks of. He almost says that aloud, rather scathingly, but it's not worth it. At the rate his mark is burning he was going to die soon and Sirius looks not too far from death's door himself.

"That's good," he says heavily instead.

Sirius nods vacantly. Then, he cracks a grin, "Guess we're on the same side of the war this time."

Regulus doesn't understand how that's a cause to grin but he grins anyway. He clasps Sirius' bony hand with his scarred one. Sirius looks at the scars and then pulls up Regulus' sleeve. He frowns. It's not the mark, but it's a lot of mangled skin.

"I'll see you around," says Regulus, pulling back his hand.

Sirius lets go, as he usually does. Regulus isn't surprised. Sirius wouldn't have let go if Regulus had been James.

"See you around," says Sirius.


	2. 2

**2**

He finds it horrifically funny when a war ensues between his brother and Kreacher. Sirius unearths a mound of old family trinkets that Regulus had completely forgotten about and was adamant on throwing it all out. Kreacher, eternally the Black family champion, bravely puts up a worthy fight. To make matters worse, the Weasleys and other members of the Order begin trickling in. Kreacher, too overwhelmed by the presence of blood-traitors, mudbloods and lycanthropes, takes to locking himself in his den.

Regulus lures him out with a treacle tart or two at night when everyone is asleep and lets him sit next to him by the fire.

Mrs Weasley comes down one night and Kreacher immediately disappears, leaving Regulus alone and unhinged beside the fire. They arrived three days ago and Regulus had steered clear of them and their red hair and their hand-me-down robes.

"I think there's a boggart in one of the rooms," she said.

"Yeah, I'm not getting rid of it," says Regulus and she gives him an irritated look.

He doesn't want to see boggarts turn into corpses and water. He has become so tired he barely thinks of that anymore.

He wonders if he should tell her about the way her twin sons almost blew up his classroom or the way they almost destroyed his desk or the way they tried to trip him down the moving staircase. Instead, he asked her if she wants some tea because he doesn't want to awkwardly sit there while she hovered, obviously worried about a boggart he can't be bothered to be afraid of.

She looks a bit surprised but says she will make it instead.

A part of him- a very old part of him that was created by habit and a lot of Black ideology being shoved down his throat- shudders at the thought of a filthy blood traitor offering to make him tea. He shuts that part up and pulls up a chair for her.

"Seven kids," he muses as the kettle boiled, "don't know how you do it."

"I don't know how I do it either," she says tiredly.

"My mother couldn't even manage two before she went around the bend."

"That portrait…" she begins, hesitant.

"That's her," nods Regulus, "in all her glory."

Mrs Weasley pours him a cup and frowns when he adds in five lumps of sugar. Funny how she'd be annoyed with that when he knew, for a fact, she thought him dangerous as a teacher anyway. A Black and a Death Eater was quite a combination.

He pulls out a vial of calming draught and pours it into the tea with shaking hands. She sees him do it, of course, but stirs her tea quietly.

"I know a good ointment," she says, "for dry skin and old scars. It's very good."

He almost laughs because it sounds to incredulous. Instead, he thinks he rather likes her and says, "sure, okay. What's it called?"

"I have some in my bag, I'll bring it down to you tomorrow," she replies. "I've used it many times on burns and cuts and all sorts. It works wonderfully. And it's always good to wear mittens, even in the house. Old houses like these can get rather cold."

Regulus doesn't understand. He furrows his brows. "Come again?"

"For the trembling," she says.

This time, he does laugh and she's smiling and he wonders if she did that on purpose. He brings her a tin of biscuits and proceeds to talk to her about the great things Bill and Charlie did when they were students instead of the misdeeds Fred and George cooked up. It makes her happy and he doesn't mind.

* * *

He didn't think he could ever miss Lockhart but he does the moment Umbridge stands up and begins her illuminating speech. He shares a look with Minerva and almost groans when he sees the pink woman waiting in the corner of his classroom. She takes no time pointing out that his brother is a mad, mass murderer and that his cousin is a deranged butcher and that his family is ingrained in the dark arts. He is teaching fourth years and they are all quiet.

"Well, it's not my problem the Ministry can't keep all their prisoners locked up in Azkaban," he says.

Her nostrils flares and she writes something angry in her clipboard and his class ends with the students looking at him with a mixture of fear and awe.

"It's a good-luck charm," says Luna Lovegood, putting what looked like a radish impaled with a paperclip on his desk. "To keep away the nargles. There's been a lot of them in class."

He doesn't say anything because, to be honest, he doesn't know what to say to that. He then decides to say thank you and she smiles at him, all vacant and odd, and twirls out of class in a cloud of blonde hair.

(He throws the radish at Umbridge's head one morning when he catches her walking down a crowded hallway. It knocks off her awful pink hat. She doesn't find the perpetrator, of course, but a group of second years see him do it and give him a high-five. He keeps the radish in his coat pocket after that, feeling very lucky indeed.)

* * *

There's a link between the Dark Lord and Harry Potter and a part of that scares him. But he has been scared for so long- of water, of dreams, of reality- that it doesn't scare him as much as he thought it would. His body already died in that cave. It lost its warmth throughout the years. Now, he feels as hollow as Barty Crouch Junior, his old friend, trapped in an empty shell of himself.

And then the mass breakout happens and he finds himself trying to find Neville Longbottom. The boy is stricken and gaunt at the breakfast table and Regulus tells him to come to his office. He doesn't know why- maybe it's because he used to play with the woman who tortured the boy's parents, maybe it's because he shared her mark, her blood- but he pulls out two butterbeers and gives the boy a book on roots and fungi.

The boy's face lights up and Regulus feels a bit sorry for giving out to him throughout the years. Then again, the boy could be thick and sometimes he couldn't even hold his wand the right way round.

"Thanks, Professor," says Neville when he walks out, looking a tad bit cheerful.

"Your wand's falling out of your pocket, Longbottom," he says.

Neville catches it before it falls, grins sheepishly, and leaves. Regulus transfigures a chair into a bucket and vomits.

* * *

That night, he doesn't sleep. He never slept well before but this time, it is especially difficult. The mark was burning and his fear was escalating and calming draught after calming draught didn't seem to be working. He goes down to Madame Pomfrey and half begs her for something stronger but she doesn't listen. She cups his cheeks and tells him to breathe.

"Pacing around won't help," she says. "I can fix you some tea but there's nothing else I can give you. The moment you start on something stronger, it'll only get worse."

"I don't care," he says.

"Well, I do," she says, and makes him a cup of tea instead.

She holds his hand and he pulls away and runs his trembling hand through his hair. A memory of dead, dead hands pulling at it flood his mind and he jumps. The tea splashes on the floor and the cup shatters. He almost begs her for something stronger but he knows she'll say no.

So, he goes to Severus. The man's thin lips curl. Regulus wishes he felt sick. He doesn't mind vomiting all over Severus shoes.

"Considered a Draught of Living Death?" says Severus lazily.

Regulus laughs ruefully. "I'm already a living dead. Got something more creative?"

Severus holds up a small vial. "Serene Serum. Take two drops- _only two_. Anymore and you'll be so serene you'll forget to breathe."

"Sounds great," he says and almost grabs it.

Severus holds it back, looking skeptical. "It won't kill you," he says, as if reading Regulus' mind, "it'll only replay your worst memories over and over again. And there's no antidote to that."

"Bezoar?" Regulus grins, feeling slightly giddy.

Severus doesn't smile. He never smiles. Regulus never liked potions to know if Severus was even telling the truth about the serum. He swallows and backs away.

"I'll keep my breath then, thanks," he says.

He drinks a vial of calming draught on his way out but it does nothing to the trembling. He sees Harry Potter go into the Potions classroom for his occlumency lessons and winces. He doesn't know who has it worse: Severus or Potter.

* * *

He almost feels sorry for Sybill when she's dismissed in front of the entire school. He finds her sobbing the staffroom, alone, after Minerva's daring rescue and almost walks away. Then, he remembers Sybil sobbing that way when he hid her divinations books all over the castle in their third year and fixes her a cup of tea instead.

"Thank you," she says and blubbers all over his shoulder.

He sits there, quite stiff, because he hates it when people touch him and because she smells like a divinations classroom and he never liked divinations. But, he lets her and gives her an awkward pat on the back.

"There now, Sybil, that's quite enough," says Minerva when she comes in, stern and severe over her glasses.

Sybil blows her nose and Regulus inches away. He remembers her hiccupping like that when he had made fun of her glasses in fourth year. He gives her an awkward pat on her knee. She blubbers all over his shoulder again and he realizes that this is why he tries so hard not to be nice.

* * *

He knows he prepped them well for the OWLs and NEWTs, even if the curriculum is skewed thanks to the Ministry.

But, Hermione Granger is so worried about the exam that she starts to make him worried. She comes into his class at least twice every day with rolls and rolls of practice questions for him to mark that he starts avoiding her whenever he can.

She does give him a beaming smile at the end of her exam, which is a relief, and he sees Potter do well. Weasley, he thinks, would've done better if he hadn't been so anxious and if he bothered to pay attention in class. His twin brothers, of course, pave a pathway of destruction and leave the Great Hall in tatters. Regulus is partly annoyed at the fact that they chose to ruin the Charms paper but, at the same time, is more than satisfied by the look of horror on Umbridge's face.

And then he finds out that a herd of centaurs have taken her.

And that his brother is dead.

Dumbledore tells him after Harry Potter has destroyed the Headmaster's office and Regulus finds himself numb.

"Thank you," he says, "for letting me know," he says, and stiffly walks away.

He doesn't think of it again. Then, he goes to Grimmauld Place for the summer and stands in front of Sirius' old room. He feels like he's fifteen years old again and Sirius had just run away. Regulus closes the door and locks it.

The Daily Prophet begins to go on and on about the Dark Lord and disappearances and Regulus wonders how he made it so far into this war. He feels a locket trembling in a locked drawer in the back of his mind, but, as he had done throughout all those years, he takes some calming draught and watches his hands tremble.

He finds himself standing in front of Sirius' locked door at night, thinking his brother is inside, reading some Muggle magazine to spite their mother or sending owls to his friends to spite their father. He knocks on the door, as he used to do, and wonders why Sirius doesn't answer.

* * *

He thinks of Andromeda when he sees Nymphadora Tonks and thinks of Andromeda again when the pink-haired woman eyes Lupin during the Order meetings. Lupin looks older and greyer and sadder than Regulus had ever seen him which, in turn, makes Tonks sad to the point that her hair turns mousy and she looks like Andromeda just before she had run away from home.

"How is your mother?" he asks her one evening, calming draught in hand, tremble in his fingers.

"She's a pain, but she's alright," says Tonks glumly. "She says you're welcome to dinner, by the way, but I wouldn't go for the cooking."

"Andromeda cooks?" he says before he can stop himself.

He reminds himself that she married a mudblood- no, _muggleborn_ , he's better than that- and that things have changed.

"She thinks she can, but Dad usually saves the day," she grins, her hair almost turning pink.

He grins back and it makes his face less like Bellatrix and more like his brother before he had been sent to Azkaban.

He locks up that night but opens the door to a tearful Narcissa. She holds his scarred hands by the fire and cries about her imprisoned husband and her cursed son.

"He's only a boy," she moans, "he's just a boy- I can't lose my boy-"

"I told you," he says, not scathingly, but tiredly, " _I told you_ , but _you don't listen_."

He has told her. Time and time again, he has told her to change because purebloods will pay the price for a supremacy they don't deserve. He had written to her about her son's slurs and Narcissa would write back with the clipped tones of Lucius Malfoy, her head inflated by her husband's ego.

He tells her to ask Severus because there's nothing he can do. He's on the run and he has to change house every three days because the Death Eaters are on his tail and Bellatrix can sniff his blood like a hound.

"Severus?" says Narcissa, big eyes brimming with tears.

"I've heard the Dark Lord favours him," says Regulus, and he doesn't add that Severus favours Dumbledore because of that red-haired mud- mugglborn with memorable green eyes. "He will help. And Draco likes him a lot more than he likes me. There's a higher chance he'll accept it."

Narcissa looks almost guilty, as if it is her fault for that- and it probably is- but Regulus leads her out the door and lets her kiss his cheek goodbye. He remembers her kissing his mouth when he was sixteen and he realizes that a useless part of him misses her.

"I'm sorry," she says and he doesn't know what she's apologizing for because they had both made so many mistakes.

"Goodnight," he says instead.

* * *

He sees Draco in school and the boy looks haggard. Severus is having no luck, it seems, and Draco seems to be spiraling into his own whirlpool of misery. Regulus tells him to stay behind after class one morning and is given a sneer the he wishes he can slap off the boy's pointed face. He gives the boy a butterbeer instead and tells him to sit down-

"I don't want to," spits Draco.

" _SIT."_

Draco sits and Regulus notices that the boy's hands are trembling. _Idiot_ , he thinks, _soft fool_ , he thinks, and that _it's your own damn fault_. He lacks sympathy and he suddenly wonders if this is what Sirius felt when Regulus had gone astray. Regulus frowns.

He pulls up his sleeves and shows Draco the mangled skin on his arms. It extends all the way up his neck, down his chest and around his legs, but Regulus, of course, can't show him all that or else he'll end up fired for stripping in front of a student. But the arms are enough, it seems, because Draco looks petrified and pale.

"And this isn't even a way out," says Regulus quietly, "because there's no way out."

Draco storms out of his classroom in tears and Regulus really can't do anything for Cissa's son. The damage has already been done and Regulus isn't even able to sort out his own damage to sort out Draco's.

* * *

Dumbledore comes to him one evening and asks him about the cave.

"Why?" he says sharply.

"Can you perhaps remember what happened?"

Regulus laughs. Of course he remembers. Then, he stops, because he really doesn't. He remembers drowning and the corpses and the frigid fear that made him wish and pray and hope and beg for death. But he remembers nothing else. He can't remember why he was there. He can't remember what he had found. The trauma had erased all that from his head to try and protect him.

Dumbledore offers him a vial. "Do you think you can place the memory here?"

Regulus doesn't take it. He looks at Dumbledore with the eyes of a scared teenager and, in a watery voice, says: "no, please… no…"

He remembers saying that to Kreacher as the elf gave him more and more cursed potion to swallow. He feels his skin prickle and he shudders. Dumbeldore's dead hand is still outstretched.

"Regulus," says the old man. "Please."

Regulus shakes his head but takes the vial.

(A week later he stops Harry Potter in the hallway, grimy from Quidditch practice, and gives him a vial of silvery liquid.

"Make sure you haven't had your dinner when you watch this," he says with a shaky smirk, "or else you'll be vomiting all over Dumbledore's office."

Harry Potter looks confused but Regulus waves him off and wishes him luck in the next game. He thinks of taking a broom and flying around the castle for a bit, as he used to do when he was a student, but schoolboy memories are like hammers when his mind is like glass.)

* * *

Regulus can't look at himself in mirrors anymore since he looks so gnarled and dead and so much like Sirius that he has to stop himself from trying to gouge his eyes out. He busies himself with grading papers and staring out at the sky because dark rooms remind him of caves.

He avoids Horace Slughorn but, of course, Horace Slughorn finds him and drags him to his Christmas party where Regulus feels exactly as he did when he was seventeen: dead, alone and scared in a world that keeps dancing around him. He cringes when he spots Hermione Granger with McLaggen and ends up talking to Luna Lovegood and showing her the radish she had given him as a good luck charm the year before.

She beams and says something about wriggle-berks and tangle-warts and he only nods because he'd much rather hear her nonsense than Slughorn's.

"Terribly sorry about Sirius," says Horace, "awful fate, awful indeed! He was such a talented boy- with potions and trouble, ho ho- I can remember a thing or two about the mischief he went up to in my classroom!"

Regulus can't even swallow the dryness in his throat but Horace gives him an encouraging thump on the back that makes him cough. He slips away and finds Minerva in her office and asks for a biscuit. She smiles and he can't remember why he never liked her as a student.

"It's because you always turned in your homework a day late," she said, "and I made you serve detention instead of Quidditch practice."

"A scheme to let your house win?"

Minerva almost grins, "perhaps." She gives him another biscuit. "I see Horace has brought his Slug Club back together."

"Yeah," Regulus hums. "They're as awful as I remember."

Slughorn used to force Sirius and Regulus to sit side by side. It was okay at first. It became horrific when Regulus, fifteen and furious, and Sirius, sixteen and seething, ended up clawing at each other like dogs. They spent their weekends polishing trophies and spitting slurs for a month.

"It'll get better," says Minerva sternly.

He hums and takes another biscuit.

* * *

He gets an invitation from Mrs Weasley to spend Christmas with them and he's faintly surprised. A remnant of him tells him that there's no way he's going to sit in a house of blood traitors and mudbloods, but he ends up accompanying Lupin only for Christmas Eve just to prove a point to himself.

He overhears Lupin talk to Harry Potter about a 'half-blood prince' and brings up James and Sirius during their school years. He pulls an inattentive Regulus into the conversation.

"You wouldn't have heard of a half-blood prince at school, did you?" asks Lupin.

Harry Potter looks at him with a mixture of curiosity and discomfort.

"Prince… they're an old pureblood family. I know one Prince ended up marrying a muggle so, I guess, whoever their child can be a 'half-blood' Prince, per se."

But Potter seems adamant it's someone because he asks: "do you remember anyone in Slytherin being called that?"

Regulus is almost annoyed. "I know some Slytherins can be a bit unbearable but we don't go walking around calling each other 'prince' and 'princess'."

Potter looks suspicious of him and Regulus almost has to wonder what the boy thinks: Death Eater, Black, brother to a godfather he loved, unapproachable, unhinged, mad, every inch his mother's son. Lupin goes to the kitchen to help Mrs Weasley and Regulus sits by the fire, itching to reach out for the coal.

"I overheard something," says Harry, "between Malfoy and Snape."

Regulus shrugs. He couldn't save his family all those years ago; he can't save them now. He is too busy trying to save himself to think of anything else.

"I'll look into it," he says, just as he had said to Hagrid when the giant asked him for pictures of James and Lily, not because he honestly cares but because he's too tired to explain otherwise.

That's the thing with people who didn't live through a war. That's the thing with people who weren't Blacks. Blacks can see a lost cause immediately. They have watched one too many young people die. So, he can see Draco's doom even though others were blind to it. Narcissa could see it too. People like Harry Potter, who have too much hope, were the type of people that don't let go. James Potter wouldn't have let go of Sirius if Sirius had been the one drowning in the lake. Regulus, who had no one, drowned all alone.

He thinks of Kreacher and sends the elf a Christmas card.

"Are you sure you don't want to stay the night?" says Mrs Weasley as he puts on his coat to leave. "You can't spend Christmas alone."

"I'm well used to it," he murmurs and thanks Merlin she didn't hear him.

He thanks her for the invitation and thanks Mr Weasley for the sympathy and wanders around in the darkness for a little bit.

* * *

Harry Potter comes to him one evening and tentatively asks about a locket. The conversation is awkward and stiff because they never really got along. He looks too much like James Potter and Regulus can't stand that. The boy repeats the question a few times because, for some reason, Regulus can't really hear the words.

"What locket?" he says, genuinely confused and Potter looks just as.

Potter is pale, "I saw the memory… with Dumbledore." Then, he tastes his words before he says them. "The cave?"

Regulus can't understand. "What cave?"

Potter is beyond confused. Regulus even more so. He runs a hand through his hair and his hands are shaking so much he has to hide them behind his back.

"In the memory," says Potter. "Dumbledore… Dumbledore thought it'd be easier if I asked you if you remember… if you remember where you put it? Or if you took it out of the cave?"

"A locket?" says Regulus.

His eyes are wide because he can see a locket- he sees two lockets- and he sees a boat and he hears chains ringing and he hears water rippling and he remembers a dead man's face floating up to the surface, silent and asleep, because Regulus hadn't touched the water yet.

Then their white, white corpses burst out of a closet, like a boggart, and he almost screams but he doesn't- because there's a scared, sixteen year old boy in his classroom and he can't break and shatter in front of him.

"I… I don't know…" he says. "Tell… tell Dumbledore I don't know. Did I…? You saw the memory, did you?" Potter tentatively nods. "Did I… Did I make it out?"

Potter looks confused. Regulus is even more so. He can't understand how he is here, wet and dry, as slimy hands and rotten teeth and broken nails try to rip him apart. He is in a classroom but his body feels empty; he's floating in a very bad dream and there is James Potter standing here in front of him, without Sirius by his side, looking at him with memorable green eyes.

"Get out," he says to Potter harshly. " _Get out_."

The boy looks at him with angry eyes.

He overhears them on their way to Transfigurations one crisp morning and almost scoffs.

"He always did look a bit mad," says Ronald Weasley, his bag falling off his shoulder, "but it's like he's vying for Witch Weekly's Most Insane Aristocrat Award this time around. Fred reckons he's a maniacal laugh away from St Mungo's."

"How about you say that a bit louder," says Harry Potter. "I think the Giant Squid didn't catch that."

* * *

He can't teach anymore and that drives the fifth and seventh years nuts but, honestly, they're going to have worse things to worry about than OWLs and NEWTs the moment the war breaks through the walls.

He paces up and down the halls and stares up at the sky in the darkening courtyard, not really able to hear anything because there's too much water in his ears. He coughs out water onto the floor and feels cold and wet and wretched.

He remembers a locket, he remembers a note- _it was I who discovered your secret- I intend to destroy it as soon as I can-_ and he remembers Kreacher and the pulsing, pounding, evil darkness manifesting itself in one of the drawers of the living room in Grimmauld Place-

He sprints to Dumbeldore's office. He's alive and he's dry and he's sane and he remembers, he remembers, he remembers-

But he comes face to face with snarling, seething Bellatrix and it feels like the cave has collapsed and he's buried under the grave of rubble and rock.

 _I killed Sirius Black- I killed Sirius Black- I killed Sirius Black-_

He evades curse after curse not because he's a skilled duelist but because he has seen her kill and torture time and time again in his dreams. Draco is watching behind her, grey eyes as wide as the moon, and Regulus can smell a barbaric lycanthrope crawl into the castle.

She gets angrier because he has always been quick. He is smarter than Sirius in the way that she can't goad him. Whereas Sirius would erupt into rage, Regulus had been goaded and teased and hurt since the day he was born: the second son, the spare, as useless as his mad mother.

A dark mark erupts from the astronomy tower and Regulus watches Dumbledore fall.

Before he could regret his regrets, he feels the curse slam into his chest. His body falls into the lake and he's surrounded by water. But the water is empty and pleasantly quiet- there is no bodies, no tongues, no teeth, no nails- and he's deaf to the screaming of his students and the cackles of his cousin and the shattering of his mind.

 _I face death in the hope that when you meet your match…_

His lungs fill with water.

 _You will be mortal once more._

* * *

 _ **I have no idea how I wrote this but I just came home one night and blurted all this out for hours and hours and hours until, 8000 words later, I said: okay.**_ _ **Regulus always needs a bit of appreciation and writers love reviews :)**_

 _ **Hope you enjoyed!**_

 _ **Oh! And keep your eyes peeled for another marauder fic sometime this week (either Remus-centric or some good old Sirius, lingering between the two...)**_


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